Turbofan Blade Design for Airflow Equalization and Noise Reduction
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Solution Overview
Problem
Conventional turbo fans in air conditioning systems suffer from uneven air-velocity distribution, turbulent flow, and increased noise due to blade design issues, including inclination and solid construction which leads to air separation and weight increase.
Innovation Solution
The turbo fan features a blade design with a 'reverse outward warp' at the front portion, a main-plate-side front-edge skirt portion forming an obtuse angle, and a projecting blade front edge that creates a triangular vane shape, facilitating airflow equalization and preventing air separation by generating a vertical vortex.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the entire blade is inclined to the rotation direction A, then air separation at the front edge is prevented, but turbulent flow and uneven air-velocity distribution occur at the rear edge portion
Solution Approach 1:
The blade design applies different inclination characteristics to different portions: the front edge portion is inclined to prevent air separation, while the rear edge portion has reduced inclination or is perpendicular to the rotation direction to suppress turbulent flow. This local differentiation resolves the contradiction by optimizing each portion for its specific function.
Solution Approach 2:
The blade is segmented into multiple portions (front edge portion, intermediate portion, rear edge portion) with different geometric characteristics. Each segment addresses specific flow conditions at its location, preventing air separation at the front while avoiding turbulent flow at the rear.
2Ease of manufacture
If the blade is made solid for structural integrity, then manufacturing is simplified, but weight increases
Solution Approach 1:
The blade employs a hollow structure with thin-walled construction, replacing solid material with shell-like geometry. This maintains structural integrity through optimized wall thickness and geometric strength while dramatically reducing weight compared to solid construction.
Solution Approach 2:
The blade incorporates curved and rounded geometric features in its hollow structure design, which provide structural strength through geometric optimization while minimizing material usage. The curved surfaces distribute stresses effectively in the thin-walled hollow construction.
3Ease of manufacture
If the blade thickness is uniform in the height direction, then manufacturing is easier, but air flow concentrates at corner portions causing increased noise
Solution Approach 1:
The blade thickness is varied locally: thicker at the root for structural support and thinner at the tip for reduced weight and improved aerodynamics. This non-uniform thickness distribution prevents flow concentration at corners while maintaining manufacturability through progressive geometry changes.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design equalizes air velocity between blades, reduces noise, and prevents air separation, resulting in improved performance and reduced weight by allowing for a hollow structure.
Implementation Method 1
a vertical vortex from the blade outer peripheral face to the inner peripheral face is generated, which draws the flow to a blade inner face
Data Source
Figure 1~2
Figure 3
Figure 4(a)~4(b)
AI summary
A blade front edge 4a of a turbo fan 1 has, between a main-plate-side blade front edge 4a1 and a shroud-side blade front edge 4a2, a projecting blade front edge 4a3 which distances away from a blade rear edge 4b (located in a rotation direction A) as it furthers away from a main plate 2 ,which curves to a position away from a rotation center O, and, in a range close to the main plate 2, a main-plate-side front-edge skirt portion 41a1 which distances away from the blade rear edge 4b and inclines away from the rotation center O as it becomes closer to the main plate 2. On the other hand, a main-plate-side blade rear edge 4b1, which is a range close to the main plate 2 of the blade rear edge 4b, is substantially perpendicular to the main plate 2 and a shroud-side blade rear edge 4b2, which is a range close to a shroud 3, is inclined so as to gradually distance away from the blade front edge 4a (behind in the rotation direction A) as it furthers away from the main plate 2.